1. Field of the Invention
The present invention generally relates to an illumination system suitable to illuminate a rectangular object to be projected such as a liquid crystal panel, a liquid crystal projector using this illumination system, and a projector using an image forming member such as a reflection-type liquid crystal panel and a dichroic prism alone having a function as a color separation/combination device.
2. Description of the Related Art
For example, Japanese Laid-Open Patent Application No. 3-11806 discloses an integrator optical system having a combination of two sets of lens arrays as an illuminating optical system for uniformly illuminating a rectangular object to be projected such as a liquid crystal panel.
In the integrator optical system, a light flux from a light source is separated by a plurality of rectangular condenser lenses constituting a first lens array so as to form secondary light source images, which then superposedly form images on a same object to be projected through a second lens array having a plurality of condenser lenses corresponding to the plurality of condenser lenses of the first lens array. They say that, by such an integrator optical system, utilization efficiency of the light from the light source is improved, and, also, it is possible to make uniform an intensity distribution on the object to: be projected. In particular, by forming each condenser lens of the first and second lens arrays to have a rectangular shape having an aspect ratio of 4:3, for example, corresponding to the aspect ratio of the rectangular object to be projected, it is possible to improve the light utilization efficiency and make uniform the intensity distribution.
On the other hand, a liquid crystal projector using a liquid crystal panel of a type of modulating a polarized light can use only one type of a polarized light of a P-polarized component and a S-polarized component. Thereby, when a light source emits a random polarized light, approximately a half the light from the light source is not used. Accordingly, the light utilization efficiency is bad. In order to improve the light utilization efficiency, various types of polarization transformation arrangements have been proposed.
The principle thereof will now be described. After a random polarized light is separated into two orthogonal polarized components (P-polarized component and S-polarized component), one thereof is rotated by 90 degrees through a xc2xd phase plate or the like so as to be one having the same polarization direction as that of the other, and the optical axes of both are made coincident. Accordingly, for example, a polarization beam splitter and a rectangular prism are both provided, and a xc2xd phase plate is disposed on the light emitting side of the polarization beam splitter or rectangular prism. By such a polarization transformation optical system arrangement, the polarized directions can be made coincident. Japanese Laid-Open Patent Application No. 7-294906 discloses an arrangement in which light from a light source is converged onto an operation surface (dielectric multi-layer film of 45xc2x0) of the polarization beam splitter through a lens plate in order to improve a transformation efficiency in this case.
However, in an arrangement in which simply a polarization beam splitter and a rectangular prism are provided together, the lateral width or longitudinal width of the entire poetical system is approximately doubled, and, therefore, a projection lens having a small F number and a very large aperture or diameter should be used. In order to solve this problem, Japanese Laid-Open Patent Application 8-304739 discloses an example of arrangement in which the integrator optical systems disclosed in Japanese Laid-Open Patent Application 3-11806 are combined. There, in summary, a plurality of minute light fluxes (secondary light-source images) are formed through a first lens array consisting of a plurality of minute rectangular condenser lenses, these light fluxes are separated into P-polarized components and S-polarized components having different polarization directions, then, the polarized components of one polarization direction are rotated so that the polarization planes thereof are made coincident, and the thus-obtained light fluxes are emitted. That is, as a result of separating of polarized light being performed by utilizing a process of generating of minute secondary light-source images which is a feature of the integrator optical system, it is possible to control spatial expansion of light paths due to separation of the polarized light.
Further, Japanese Laid-Open Patent Application No. 10-161065 discloses to condense parallel light from a light source through a convex lens, then, transform the light into parallel light again, and, thereby, to make the beam diameter approximately half, and direct it to a polarization transformation arrangement. Thereby, the polarization transformation arrangement and integrator optical system can be substantially miniaturized.
However, these arrangements have problems in that the arrangement of the integrator optical system is complex and thereby difficult to be manufactured, efficiency in polarization alignment is not sufficient, and so forth.
For example, with regard to the integrator optical system, each of the first and second lens arrays should be formed to a special shape having many lens elements to the amount of mxc3x97n pieces like a two-dimensional array. Therefore, it is difficult to make them. Further, it is not easy to manufacture them correspond to the aspect ratio such as 4:3 of a liquid crystal panel.
Further, when, as disclosed in Japanese Laid-Open Patent Application No. 8-304739, a polarization aligning arrangement is disposed subsequent to the second lens array in order to make polarization directions coincident, the second lens array condenses light two-dimensionally (not only in the width direction of the polarization beam splitters but also in the longitudinal direction, being separated into a plurality of divisions) although polarization beam splitters and so forth of the polarization aligning arrangement are formed to be like an array. Therefore, the power in the condensing part is large and the load (stress) on the polarization beam splitters is large. Furthermore, it is difficult to make an arrangement such that correspondence is secured between the polarization beam splitter row, total reflection mirror row and one array of the second lens array.
Generally, there are various types of projectors. For example, in comparison to using a transmission-type liquid crystal panel, by using a reflection-type liquid crystal panel, it is easy to obtain high resolution and high luminance, and, also, it is possible to use a single optical component both as a color separating component and a color combining component, thereby miniaturization thereof being able to be achieved.
When such a reflection-type liquid crystal panel is used in a projector, a polarization beam splitter and a dichroic mirror as a color separation/color combining component disposed on incident and emitted light paths are used, color separation of light from a light source and color combination of modulated light reflected by the reflection-type liquid-crystal panels for respective colors are performed, the thus-obtained light is incident on a projection lens system so that a projected color image is obtained, as disclosed in Japanese Laid-Open Patent Application No. 3-249639.
FIG. 1 shows a proposed example of a liquid crystal projector using such a basic idea using reflection-type liquid-crystal panels. This liquid crystal projector includes a light source 101, an illumination system 102, a total reflection prism 103, a connection prism 104, a polarization beam splitter 105, a color separation/color combination component 106, three reflection-type liquid crystal panels 107R, 107G and 107B, and a condenser lens 108 for each of the reflection-type liquid crystal panels 107R, 107G and 107B. The light source 101 includes a lamp 109 and an ellipse surface mirror 110. The illumination system 102 includes a total reflection mirror 111 for deflecting a light path, a collimator lens 112, a pair of fly-eye lens plates 113, 114 forming an integrator optical system, a polarization aligning prism array 115, and a condenser liens 116. The integrator optical system is well known from Japanese Laid-Open Patent Application No. 3-11806 and so forth.
The polarization beam splitter 105 is disposed on a superposed incident/emitted light path, and reflects an S-polarized component of light incident thereon from the illumination system 102 by 90xc2x0 toward the color separation/color combination component 106. A dichroic prim is used as the color separation/color combination component 106. This dichroic prism 106 is formed to be an optical element having a cubic shape or rectangular-parallelepiped shape in which a dichroic film 106r for red having a property of reflecting a long-wave-length range of red light R so as to separate the long-wave-length range of red light R and a short-wave-length range than green light G and a dichroic film 106b for blue having a property of reflecting a shortwave-length range of blue light B so as to separate the short-wave-length range of blue light B and a long-wavelength range than the green light G are disposed orthogonally. Accordingly, the dichroic prism 106 has the dichroic film 106r for red parallel to the reflective surface 105a of the polarization beam splitter 105 and the dichroic film 106b for blue perpendicular to the dichroic film 106r for red formed therein. These dichroic films 106r and 106b are formed as dielectric multi-layer films.
The three reflection-type liquid crystal panels 107R, 107G and 107B are disposed correspondingly to the dichroic film 106r for red and dichroic film 106g for green of the dichroic prism 106. That is, the reflection-type liquid crystal panel 107R is disposed in the direction in which the light of wavelength equal to or longer than the red light R is reflected by the dichroic film 106r, the reflection-type liquid crystal panel 107B is disposed in the direction in which the light of wavelength equal to or shorter than the green light G is reflected by the dichroic film 106b, and the reflection-type liquid crystal panel 107G is disposed in the direction in which the light is transmitted by the dichroic film 106r for red and dichroic film 106b for blue. These reflection-type liquid crystal panels 107R, 107G and 107B have images of respective colors formed therein to be projected formed through ON/OFF control of respective liquid crystal elements thereof by an information display system (not shown in the figure).
Further, a projection lens system 119 having a projection lenses 118 is provided on the emitted light path between the polarization beam splitter 105 and a screen 117. There, light paths from a virtual light-source surface provided by the integrator optical system to the respective reflection-type liquid crystal panels 107R, 107G and 107B are approximately equal to each other, and the light paths between the respective reflection-type liquid crystal panels 107R, 107G and 107B and projection lens 118 are approximately equal to each other.
In this arrangement, the light flux caused to have only the S-polarized component from the illumination system 102 is directed by the total reflection prism 103 and polarization beam splitter 105, and is incident on the dichroic prism 106. There, the incident light is separated into the red,light R, green light G and blue light B in accordance with the wavelengths thereof, and these lights are incident on the respective reflecting liquid crystal panels 107R, 107G and 107B. The respective reflection-type liquid crystal panels 107R, 107G and 107B are turned on and off in accordance with image signals input to the liquid crystal projector from the information display system. When they are turned off, the S-polarized light component is reflected thereby as it is. When they are turned on, the S-polarized light component is reflected thereby being transformed (modulated) into the P-polarized light component. The light including the S-polarized light component and P-polarized light component reflected by the respective reflection-type liquid crystal panels 107R, 107G and 107B is collected and combined by the dichroic prism 107, respectively, and returns to the polarization beam splitter 105. At this time, only the P-polarized component reflected by each of the respective reflection-type liquid crystal panels 107R, 107G and 107B at turned on liquid crystal elements thereof is transmitted by the polarization beam splitter 105. Thereby, the thus-transmitted light is magnified and projected onto the screen 117 through the projection lens system 119. Thereby, an image in accordance with the image signals input to the liquid crystal projector is displayed on the screen as a color image.
Thus, the dichroic prism 106 is used for both color separation and color combination. Thereby, it is possible to miniaturize the entirety.
However, with regard to the dichroic prism 106, it is not possible to provide the dichroic film 106r for red and dichroic film 106b for blue having properties of efficiently reflecting the P-polarized light components and S-polarized light components in the same degree. Thereby, when the function of separating the light coming from the illumination system 102 into the red light R, green light G and blue light B, and the function of combining the light obtained as, a result of the thus-separated lights being modulated by the reflection-type liquid crystal panels 107R, 107G and 107B for the respective colors are executed by the same dichroic prism 106, the performance is very bad in comparison to a case of a projector in which color separation and color combination are performed by separate optical components.
This matter will now be described in more detail. When polarization characteristics of a dichroic prism on the market were examined, results shown in FIGS. 2A and 2B were obtained. FIG. 2A shows reflection characteristics for blue light B of the dichroic film 106b for blue and FIG. 2B shows reflection characteristics for red light R of the dichroic film 106r for red, as polarization characteristics for P-polarized light components, S-polarized light components and P*S light. It can be seen therefrom that, in any case, the reflection characteristic varies depend on the polarization state of the incident light. In particular, the reflectivity for the P-polarized light components is low.
This dichroic prism was used as a dichroic prism for color combination for transmission-type liquid crystal panels 121R, 121G and 121B on which light obtained from color separation performed by another optical component were incident respectively, as shown in FIG. 3A. Then, S-polarized light was obtained from the color combination. In this case, the polarization combination characteristics are shown in FIG. 3B. Thus, the characteristics were superior, as shown in the figure.
However, when the dichroic prism was used as the dichroic prism 106 for color separation/color combination for the reflection-type liquid crystal panels 107R, 107G and 107B, as shown in FIG. 4A, and the characteristics of separation of a S-polarized light component and combination of a P-polarized light component were examined, the intensities of red light R and blue light B were low, and a color image having a sufficient color balance could not be obtained, in the separation/combination by the same dichroic prism 107 used for both purposes, as shown in FIG. 4B.
An object of the present invention is to provide an illumination system and a liquid crystal projector in which arrangements thereof are simplified and thereby manufacture thereof is easy without the function required for the integrator optic al system being degraded.
Another object of the present invention is to provide an illumination system and a liquid crystal projector having a superior property in matching with a polarization alignment arrangement for making polarization directions coincident and which can reduce a load on a polarization separating prism of the arrangement.
Another object of the present invention is to provide a projector which can be miniaturized and made to have a light weight as a result of a dichroic prism which can achieve, in a condition in which there is almost no difference in intensity therebetween, a color separating function of separating incident light into red light, green light and blue light, and a color combining function of combining the thus-separated color light being used as a color separation/color combination component in a condition in which there is no problem in optical characteristics in comparison to a case of transmission-type liquid crystal panels.
Another object of the present invention is to provide a projector using a dichroic prism which can achieve a color balance and light utilization efficiency in no way inferior to a case where separate optical components are used for performing color separating function and color combining function by having a filtering function such that a polarized component of one of P-polarization and S-polarization has a fixed shift in characteristics thereof with respect to a polarized component of the other one.
Another object of the present invention is to provide a projector which can prevent keystoning.
Another object of the present invention is to provide a projector which can be miniaturized, have a light weight, and a reduced luminance variation.
Another object of the-present invention is to provide a projector which is small-sized, has a light weight, has a high light utilization efficiency of a light-source light, and displays a bright projected image.
An illumination system according to the present invention comprises:
at least one light-emitting unit;
at least one reflecting mirror for condensing light;
a lens plate disposed on the side of an object to be projected with respect to the reflecting mirror, having a plurality of lens elements arranged two-dimensionally, approximately perpendicular to a main optical axis of a projection lens system and the object to be projected, each having a shape approximately similar to a shape of the object to be projected and approximately the same as each other, for dividing light into a plurality of light fluxes;
a first lenticule having a plurality of cylindrical lenses arranged and disposed at or near a position to which light passing through the respective lens elements of the lens plate is condensed;
a second lenticule disposed subsequent to the first lenticule and having a plurality of cylindrical lenses arranged in a direction perpendicular to the direction in which the plurality of cylindrical lenses of the first lenticule are arranged; and
at least one convex lens disposed so as to refracting the light path of the light flux formed by each of the plurality of lens elements of the lens plate so that the light flux illuminates the entire surface of the object to be projected after passing through the first and second lenticules.
Accordingly, instead of a so-called second lens array of an integrator optical system for reducing an expansion of the secondary light-source images acting as the virtual light source for illuminating the object to be projected, the first and second lenticules having array structures of cylindrical lenses are used. Thereby, it is possible to reduce the number of necessary lenses from mxc3x97n into m+n, and, also, manufacture of these lenticules is easy because each has the array structure of cylindrical lenses merely in one direction. Further, it is possible to deal with the aspect ratio of the object to be projected, such as a liquid crystal panel or the like by the combination of the first and second lenticules. Accordingly, in comparison to the second lens array, it is easy to deal with the aspect ratio.
The reflection mirror may comprises a spheroid mirror having the light-emitting unit disposed therein at or near a first focal point thereof;
the device may further comprise another convex lens disposed outside of a second focal point of the spheroid mirror; and
the lens plate may be disposed on the side of the object to be projected with respect to the other convex lens.
Accordingly, even in the arrangement in which the spheroid mirror is used in the light source part, the same advantages are obtained. In particular, as a result of the spheroid mirror being used as the reflection mirror of the light source part, the light emitting unit being disposed at the first focal point thereof and the convex lens being disposed outside of the second focal point, it is possible to cause the light to be transformed into a parallel light flux through the convex lens and then incident on the first lens array of the integrator optical system after the light from the light emitting unit is efficiently condensed toward the second focal point by the spheroid mirror. Thereby, it is possible to improve the optical characteristics in comparison to the case where the light is transformed into a parallel light flux as a result of a concave lens being inserted on a light path through which the light is condensed toward the second focal point. And also, it is possible to reduce an expansion of the secondary light-source images acting as the virtual light source for illuminating the object to be projected to the utmost. Thus, the present arrangement is advantageous for reducing the apertures/diameters of the projection lenses in the condition in which the spatial distance between the light emitting unit and the object to be projected is short.
An illumination system according to another aspect of the present invention comprises:
at least one light-emitting unit;
a unit forming an approximately parallel light;
a unit condensing the approximately parallel light and forming a focal point;
a first convex lens disposed outside of the focal point;
a lens plate disposed on the side of an object to be projected with respect to the first convex lens, having a plurality of lens elements arranged two-dimensionally, approximately perpendicular to a main optical axis of a projection lens system and the object to be projected, each having a shape approximately similar to a shape of the object to be projected and approximately the same as each other, for dividing light into a plurality of light fluxes;
a first lenticule having a plurality of cylindrical lenses arranged and disposed at or near a position to which light passing through the respective lens elements of the lens plate is condensed;
a second lenticule disposed subsequent to the first lenticule and having a plurality of cylindrical lenses arranged in a direction perpendicular to the direction in which the plurality of cylindrical lenses of the first lenticule are arranged; and
at least one second convex lens disposed so as to refracting the light flux formed by each of the plurality of lens elements of the lens plate so that the light flux illuminates the entire surface: of the object to be projected after passing through the first and second lenticules.
Accordingly, also in an arrangement in which at least one light emitting unit, a unit forming approximately parallel light, a unit condensing the approximately parallel light and forming a focal point and a first convex lens disposed outside of the focal point are used in a light source part, for example, in an arrangement in which a parabolic mirror or a spheroid mirror is used, the same advantages are obtained.
The device according to the other aspect of the present invention may further comprise a polarization aligning prism array having polarization separating prisms and total reflection prisms arranged alternately, and xcex/2-phase-difference plates arranged for light fluxes of one type of two types obtained from the polarization separating prisms, wherein the particular cylindrical lenses of the first lenticule are made to correspond to the particular polarization separating prisms, an arrangement is made such that all the light fluxes passing through the particular cylindrical lenses pass through approximately the corresponding polarization separating prisms, and, thus, random light fluxes are made to be of polarized components of only one type,
wherein the second lenticule is disposed subsequent to the polarization aligning prism array.
Accordingly, by combining a polarization alleging prism array which makes random light fluxes be of polarized components in one type, because the polarization separating prisms and so forth of the polarization aligning prism array are formed to have an array-like structure and correspondingly thereto the respective cylindrical lenses of the first lenticule condense the light only in one direction, it is possible to reduce power in the portion toward which the light is condensed, and to reduce the load (stress) on the polarization separating prisms. And also, it is easy to make an arrangement such that a respective one of the polarization separating prisms and a respective one of the total reflection prisms correspond to each of the cylindrical lenses of the first lenticule.
The at least one reflection mirror may comprise a spheroid mirror having the light-emitting unit disposed therein at or near a first focal point thereof;
the device may further comprise another convex lens disposed outside of a second focal point of the spheroid mirror; and
the lens plate may be disposed on the side of the object to be projected with respect to the other convex lens.
Accordingly, also in the arrangement in which the spheroid mirror is used in the light source part, the same advantages are obtained.
The device having at least one light emitting unit, a unit forming approximately parallel light, a unit condensing the approximately parallel light and forming a focal point and first convex lens disposed outside of the focal point in a light source part may further comprise a polarization aligning prism array having polarization separating prisms and total reflection prisms arranged alternately, and xcex/2-phase-difference plates arranged for light fluxes of one type of two types obtained from the polarization separating prisms, wherein the particular cylindrical lenses of the first lenticule are made to correspond to the particular polarization separating prisms, an arrangement is made such that all the light fluxes passing through the particular cylindrical lenses pass through approximately the corresponding polarization separating prisms, and, thus, random light fluxes are made to be of polarized components of only one type,
wherein the second lenticule is disposed subsequent to the polarization aligning prism array.
Accordingly, also in an arrangement in which at least one light emitting unit, a unit forming approximately parallel light, a unit condensing the approximately parallel light and forming a focal point and first convex lens disposed outside of the focal point are used in a light source part, for example, in an arrangement in which a parabolic mirror or a spheroid mirror is used, the same advantages are obtained.
The first lenticule may have an aperture width of at least one cylindrical lens at and/or near the center thereof made larger than the others.
Accordingly, because, when the light source of the light emitting unit cannot be regarded as a pointy source, the energy around the center is large and blur occurs, and, thereby, the light fluxes are likely to expand around the center, it is possible to obtain total balance by enlarging the aperture width of the cylindrical lenses there.
The second lenticule may have an aperture width of at least one cylindrical lens at and/or near the center thereof made larger than the others.
Accordingly, because, when the light source of the light emitting unit cannot be regarded as a pointy source, the energy around the center is large and blur occurs, and, thereby, the light fluxes are likely expand around the center, it is possible to obtain total balance by enlarging the aperture width of the cylindrical lenses there.
The first lenticule may have, an aperture width of at least one cylindrical lens at and/or near the center thereof made larger than the others; and
the polarization aligning prism array may have a size of a pair of prisms changed correspondingly to the aperture width of the at least cylindrical lens of the first lenticule.
Accordingly, in the arrangement in which the polarization aligning prism array is provided, it is possible to cause the polarization aligning function to be performed sufficiently when the aperture widths of the cylindrical lenses around the center are enlarged.
The polarization aligning prism array may have polarization separating prisms arranged symmetrically at the center thereof, and total reflection prisms arranged outside thereof, thus the entirety of the polarization aligning prism array including further outside thereof being symmetrical.
Accordingly, in the arrangement in which the polarization aligning prism array is provided, it is possible to cause the polarization aligning function to be performed sufficiently when the aperture widths of the cylindrical lenses around the center are enlarged. And also, because the symmetrical structure is employed, it is easy to manufacture the polarization aligning prism array.
The device may further comprise a polarization aligning unit comprising a combination of a polarization separating prism, a total revelation prism and a xcex/2-phase-difference plate, disposed on the side of the object to be projected with respect to the reflection mirror for condensing light and making random light fluxes be of polarized components of one type,
wherein the lens plate is disposed on the side of the object to be projected with respect to the polarization aligning unit.
Accordingly, the two polarization aligning units are provided and two steps of polarization aligning process are performed therethrough, the degree (purity) of polarization aligning is increased, and, thereby, it is possible to increase the light utilization efficiency.
The at least one reflection mirror may comprise a spheroid mirror having the light-emitting unit disposed therein at or near a first focal point thereof; and
the device may further comprise another convex lens disposed outside of a second focal point of the spheroid mirror.
Accordingly, even in the arrangement in which the spheroid mirror is used in the light source part, the same advantages are obtained. In particular, as a result of the spheroid mirror being used as the reflection mirror of the light source part, the light emitting unit being disposed at the first focal point thereof and the convex lens being disposed outside of the second focal point, it is possible to cause the light to be transformed into a parallel light flux through the convex lens and then incident on the first lens array of the integrator optical system after the light from the light emitting unit is efficiently condensed toward the second focal point by the spheroid mirror. Thereby, it is possible to improve the optical characteristics in comparison to the case where the light is transformed into a parallel light flux as a result of a concave lens being inserted on a light path through which the light is condensed toward the second focal point. And also, it is possible to reduce an expansion of the secondary light-source images acting as the virtual light source for illuminating the object to be projected to the utmost. Thus, the present arrangement is advantageous for reducing the apertures/diameters of the projection lenses in the condition in which the spatial distance between the light emitting unit and the object to be projected is short.
Also the device according to the abovementioned other aspect of the present invention may further comprise, in addition to the polarization aligning prism array, a polarization aligning unit comprising a combination of a polarization separating prism, a total revelation prism and a xcex/2-phase-difference plate, and making random light fluxes be polarized components of one type,
wherein the lens plate is disposed on the side of the object to be projected with respect to the polarization aligning unit.
Accordingly, the two polarization aligning units are provided and two steps of polarization aligning process are performed therethrough, the degree (purity) of polarization aligning is increased, and, thereby, it is possible to increase the light utilization efficiency.
A central wavelength of the xcex/2-phase-difference plate of the polarization aligning unit may coincide with a central wavelength of the: xcex/2-phase-difference plates of the polarization aligning prism array.
Accordingly, although depending on the light emitting unit and utilization purpose, by making the central wavelength of the xcex/2-phase-difference plates of the two polarization aligning units be equal, it is possible to sharpen the polarization aligning characteristics, and, also, to increase the degree (purity) of polarization alignment.
A central wavelength of the xcex/2-phase-difference plate of the polarization aligning unit and a central wavelength of the xcex/2-phase-difference plates of the polarization aligning prism array may be caused to differ to the amounts of xc2x1 a predetermined wavelength from a green wavelength, respectively.
Accordingly, although depending on the light emitting unit and utilization purpose, by making the central wavelength of the xcex/2-phase-difference plate of the polarization aligning unit and the central wavelength of the xcex/2-phase-difference plates of the polarization aligning prism array be different to the amounts of xc2x1 a predetermined wavelength from a green wavelength, respectively, it is possible to increase the polarization transformation performance otherwise decreasing at both sides, and, as a result, to uniform the polarization characteristics by defining a wavelength band through which the function is performed. For example, xc2x150 nm are the amounts of xc2x1 the predetermined wavelength, and, thereby, the polarization aligning function is performed for the wavelength band of approximately 500 through 600 nm.
A liquid crystal projector according to the present invention comprises:
at least one liquid crystal panel in which an image to be projected is formed by an information display system;
the illumination system described above illuminating the liquid crystal plate regarded as the object to be projected; and
a projection lens system for,projecting the image formed in the liquid crystal panel onto a screen.
Accordingly, because any of the above-described illumination systems is used for illuminating the liquid crystal panel, it is possible to illuminate the liquid crystal panel through the illumination system having the entirely simple structure, to perform projection onto the screen through the projection lenses having the reduced apertures/diameters, and to miniaturize the entirety of the liquid crystal projector.
The liquid crystal panel used there may be either a reflection-type one or a transmission-type one. Further, in a case of color display, ordinary, three liquid crystal panels for three primary colors, RGB (red, green and blue) are used together with a spectro device such as a dichroic prism or mirror and so forth, for example.
A projector according to another aspect of the present invention comprises:
three reflection-type image forming members for forming an image to be projected by modulating a polarization state for each color region of a red region, a green region and a blue region;
a light source emitting light for illuminating the image forming menders;
a polarization beam splitter disposed on a light path comprising both an incident light path from the light source to the image forming members and an emitted light path from the image forming members to a projection lens system, reflecting one of P-polarized light and S-polarized light from the light source and transmitting the other thereof in an approximately 90xc2x0 different direction; and
a dichroic prism disposed on a light path between the polarization beam splitter and the three image forming members, and having a dichroic film for red separating a long wavelength band of red light from a wavelength band shorter than green light and a dichroic film for blue separating a short wavelength band from a wavelength band longer than the green light, the dichroic prism acting a color separating/color combining device having both a function of separating the light of the polarized component of one type obtained from the polarization beam splitter into a red region, a green region and a blue region and directing them to the corresponding image forming members, and a function of combining light of the respective regions having the polarization states modulated by the image forming members and then incident again thereto, wherein the dichroic film for red has the maximum reflectivity for a polarized component in one of S-polarization or P-polarization of the red light is equal to or higher than 80% of the maximum reflectivity thereof for a polarized component in the other polarization of the red light, and the dichroic film for blue has the maximum reflectivity for a polarized component in one of S-polarization or P-polarization of the blue light is equal to or higher than 80% of the maximum reflectivity thereof for a polarized component in the other polarization of the blue light
Accordingly, with regard to the dichroic prism used as the color separating/color combining device, by using one having the dichroic film for red and dichroic film for blue having equivalent characteristics such that each thereof has the maximum reflectivity for one of S-polarized light or P-polarized light of corresponding color equal to or higher than 80% of the maximum reflectivity for the other polarized light as a result of a special arrangement concerning multi-layer films being made for those films, the polarization dependency is reduced, it is possible to equalize the reflection characteristics for polarized components when color separation is performed to the reflection characteristics for polarized components when color combination is performed such that the light modulated by reflection-type liquid crystal panels :as the image forming members and again incident is combined. Thereby, it is possible to use the single device to perform the functions of the color separating/color combining device by which commercial-values can be secured. As result, it is possible to miniaturize and reduce in weight the entirety of the projector.
A projector according to another aspect of the present invention comprises:
three reflection-type image forming members for forming an image to be projected by modulating a polarization state for each color region of a red region, a green region and a blue region;
a light source emitting light for illuminating the image forming menders;
a polarization beam splitter disposed on a light path comprising both an incident light path from the light source to the image forming members and an emitted light path from the image forming members to a projection lens system, reflecting one of P-polarized light and S-polarized light from the light source and transmitting the other thereof in an approximately 90xc2x0 different direction; and
a dichroic prism disposed on a light path between the polarization beam splitter and the three image forming members, and having a dichroic film for red separating a long wavelength band of red light from a wavelength band shorter than green light and a dichroic film for blue separating a short wavelength band from a wavelength band longer than the green light, the dichroic prism acting a color separating/color combining device having both a function of separating the light of the polarized component of one type obtained from the polarization beam splitter into a red region, a green region and a blue region and directing them to the corresponding image forming members, and a function of combining light of the respective regions having the polarization states modulated by the image forming members and then incident again thereto, wherein 10 nm xe2x89xa6|xcex50Pxe2x88x92xcex50S|xe2x89xa650 nm, where xcex50P represents the wavelength at which the reflectivity of the dichroic film for red for P-polarized light becomes 50% and xcex50S represents the wavelength at which the reflectivity thereof for S-polarized light becomes 50% in the wavelength band of 550 nmxe2x89xa6xcexxe2x89xa6700 nm, and, also, 10 nmxe2x89xa6|xcex50Pxe2x88x92xcex50S|xe2x89xa650 nm, where xcex50P represents the wavelength at which the reflectivity of the dichroic film for blue for P-polarized light becomes 50% and xcex50S represents the wavelength at which the reflectivity thereof for S-polarized light becomes 50% in the wavelength band of 400 nmxe2x89xa6xcexxe2x89xa6550 nm.
Same as the above, with regard to the dichroic prism used as the color separating/color combining device, the difference in the polarization dependency of the dichroic film for red and dichroic film for blue should be reduced. However, although it is preferable to equalize the polarization dependencies of these dichroic films, it is not possible to completely equalize them. Therefore, as a result of an arrangement is made for the films such that the films have filtering functions in which the shift amount of the characteristic for one polarized component with respect to the characteristic for the other polarized component is controlled within a fixed amount, it is possible to perform color combination with a color balance in no way inferior to a case where separate optical components are used for providing color separating function and color combining function, and to increase the light utilization efficiency.
The dichroic prism may have the dichroic film for red and dichroic film for blue arranged orthogonally, and, also, an incidence surface of the polarization beam splitter may be approximately perpendicular to incidence surfaces of these dichroic films.
Accordingly, by making an arrangement such that an incidence surface of the polarization beam splitter is approximately perpendicular to incidence surfaces of these dichroic films, allowance in incidence angle increases, and the light utilization efficiency can be increased. Thereby, it is possible to perform a design more advantageously.
The dichroic prism may have the dichroic film for red and dichroic film for blue arranged orthogonally, and, also, incident light may be incident on the dichroic film for red and dichroic film for blue with approximately equal shift angles.
Accordingly, as a result of shifting the image forming members in a direction perpendicular to the optical axis, and making an arrangement such that incident light may be incident on the dichroic film for red and dichroic film for blue with approximately equal shift angles, it is possible to prevents keystoning from occurring on the screen.
The dichroic prism may have the dichroic film for red and dichroic film for blue arranged orthogonally, and, also, an arrangement may be made such that incident light is incident on one of the dichroic film for red and dichroic film for blue with a predetermined incidence angle smaller than 45xc2x0 while the incident light is incident on the other dichroic film with a predetermined incidence angle equal to or larger than 45xc2x0.
Accordingly, same as the above, it is possible to prevent keystoning from occurring on the screen. Further, in particular, by shifting the incident light in a direction perpendicular to the intersecting line on which the dichroic film for red and dichroic film for blue of the dichroic prism intersect, it is possible to obtain the performance equivalent to the case where the incident light is not shifted, by modifying the characteristics of the dichroic films in consideration of the amount of inclination of the chief ray of the illuminating light made in order to shift the incident light.
The projector may further comprise an illumination system having at least one pair of fly-eye lens plates on an incident light path from the light source to the polarization beam splitter.
Accordingly, in configuring any of the above-described projectors, as a result of providing the illumination system employing the so-called integrator optical system on the incident light path, it is possible to illuminate the image forming members each having the approximately rectangular shape without unevenness in illumination, and to improve the quality of the projected image.
The projector may further comprises an illumination system having at least one fly-eye lens plate, a first lenticule having a plurality of cylinder lenses arranged and disposed at or near a position to which light passing through the fly-eye lens plate is condensed, and a second lenticule disposed subsequent to the first lenticules and having a plurality of cylindrical lenses arranged in a direction perpendicular to a direction in which the plurality of cylindrical lenses of the first lenticule are arranged, on an incident light path from the light source to the polarization beam splitter.
Accordingly, in configuring any of the above-described projectors, as a result of providing the illumination system employing the so-called integrator optical system on the incident light path, it is possible to illuminate the image forming members each having the approximately rectangular shape without unevenness in illumination, and to improve the quality of the projected image.
The projector may further comprise a polarization aligning device on a light path between the first and second lenticules, the polarization aligning device making random light fluxes be of polarized components of only one type.
Accordingly, in configuring any of the above-described projectors, as a result of providing the polarization alleging device in the illumination system, it is possible to use almost all of the light from the light source for illuminating the image forming members, to increase the light utilization efficiency, and to achieve high-luminance projecting display
Other objects and further features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.